Operating mechanism for a multiple interrupter unit circuit breaker

ABSTRACT

A high-voltage circuit breaker comprising a plurality of separate interrupter units connected in series, each unit comprising a set of main contacts, the series combination of a resistor and resistor switch in parallel with the main contacts, and an actuator for operating the main contacts. The actuator of one of these units operates the resistor switch of this particular unit and is mechanically linked with the resistor switches of all the other units so that the contacts of the other resistor switches are closed by the closing action of this one actuator. The resistor switches are opened in synchronism, each one by the actuator of its unit during contacts-opening action. During a circuit interruption, all the main contacts open simultaneously, placing all the resistors in series in the line; a few milliseconds later all the resistor switches open simultaneously to complete the opening cycle. During closing, the main contacts of the one unit close first, after which all the resistor switches close simultaneously, placing the resistors of the other units in series in the line; a few milliseconds later the main contacts of the other units close simultaneously to complete the closing cycle.

United States Patent inventor James Butler Peterborough, Ontario, Canada Appl. No. 19,342 Filed Mar. 13, 1970 Patented Jan. 4, 1972 Assignee Canadian General Electric Limited.

Toronto, Canada Priority Nov. 12, 1969 Canada 067,165

OPERATING MECHANISM FOR A MULTIPLE INTERRUPTER UNIT CIRCUIT BREAKER 7 Claims, 2 Drawing Figs.

0.8. Ci. 200/14511, 200/148 R, 200/ 144 AP, 200/ 146 Int. Cl. H0111 33/14 Field oi Search... 200/ 148, 148 B, 146,145,144 AP References Cited UNITED STATES PATENTS 3,256,414 6/1966 Giammona et al.... 200/ 148 B 3,390,239 6/ 1968 Miller ZOO/146 Primary Examiner-Robert S. Macon Attorneys-J. Wesley Haubner, William Freedman, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: A high-voltage circuit breaker comprising a plurality of separate interrupter units connected in series, each unit comprising a set of main contacts, the series combination of a resistor and resistor switch in parallel with the main contacts, and an actuator for operating the main contacts. The actuator of one of these units operates the resistor switch of this particular unit and is mechanically linked with the resistor switches of all the other units so that the contacts of the other resistor switches are closed by the closing action of this one actuator. The resistor switches are opened in synchronism, each one by the actuator of its unit during contacts-opening action. During a circuit interruption, all the main contacts open simultaneously, placing all the resistors in series in the line; a few milliseconds later all the resistor switches open simultaneously to complete the opening cycle. During closing, the main contacts of the one unit close first, after which all the resistor switches close simultaneously, placing the resistors of the other units in series in the line; a few milliseconds later the main contacts of the other units close simultaneously to complete the closing cycle.

PATENTEU JAN 4 I972 SHEET 1 BF 2 1\VE\IOR. JAMES BUTLER PATENTED JAN 4 I972 SHEET 2 BF 2 INVENTOR JAMES BUTLER MM 9mm.

OPERATING MECHANISM FOR A MULTIPLE INTERRUPTER UNIT CIRCUIT BREAKER This invention relates to a high-voltage circuit breaker comprising a plurality of separate interrupter units connected in series, and in particular to mechanism for controlling operation of the resistor switches forming a part of the interrupter units.

In applications of fluid blast circuit breakers where the voltage is too high for a single interrupter unit, a number of units are connected in series in order to share the voltage. A typical airblast breaker of this character uses a number of separate units connected in series wherein each unit is mounted on a pedestal consisting of a base and a column of one or more post-type porcelain insulators standing upright on the base. The interrupter unit is of a type which has a metal tank that is at full line voltage and contains a moderate volume of highly compressed dry air. The tank also houses a set of main and resistor switch contacts, a pneumatic actuator for opening and closing the contacts, and a control valve for controlling the operation of the actuator. The compressed air is used tov operate the actuator and extinguish the are generated when the contacts open. An interrupter unit of this general character is described in U.S. Pat. Nos. 2,911,546, Oppel and 3,390,239, Miller.

In a typical circuit breaker of the type shown in the Miller patent, opening is effected by operating the control valves of the interrupting units substantially simultaneously to cause the actuators in the interrupter units to open the main contacts of the units substantially simultaneously, thus placing the resistors in series in the line. A few milliseconds later, the resistor switches are opened substantially simultaneously to interrupt current through the resistors and complete the opening operation. Closing of this circuit breaker is effected by first closing the resistor switches substantially simultaneously to preinsert the resistors, after which the main contacts are closed substantially simultaneously to short out the resistors and complete the closing operation.

The resistors serve during opening to limit the peak surge voltages developed and also to reduce the rate of rise of the recovery voltage, thereby making it easier for the circuit breaker to complete the interrupting operation. During closing, the preinserted resistors serve in a known manner to reduce the magnitude of the voltage surge resulting from closmg.

One problem involved in using the same resistors for closing as for opening is that a higher value of resistance is desirable for opening than for closing. When the opening resistance is reduced to values approaching the ideal for closing, the resistor current on opening becomes so high that its interruption becomes difficult and resistor heating problems are encountered.

An object of the present invention is to provide difi'erent values of resistance for use in opening and in closing, yet without requiring separate resistor switches or separate resistors for each type of operation.

In carrying out my invention in one form, I provide a plurality of separate interrupter units connected in series, each unit comprising a set of main contacts, the series combination of a resistor and resistor switch connected in parallel with the main contacts, and an actuator for opening and closing the main contacts. The actuator of one of these units operates the resistor switch of this particular unit and is mechanically linked with the resistor switches of all the other units so that the contacts of the other resistor switches are closed by the closing action of this one actuator. The resistor switches are opened in synchronism, each one by the actuator of its unit during contacts opening action. During a circuit interruption, all the main contacts open simultaneously, placing all the resistors in series in the line; a few milliseconds later all the resistor switches open simultaneously to complete the opening cycle. During closing, the main contacts of the one unit close first, after which all the resistor switches close simultaneously, placing the resistors of the other units in series in the line; a few milliseconds later the main contacts of the other units close simultaneously to complete the closing cycle.

A better understanding of the invention may be had from the following description of the specific embodiment shown in the accompanying drawings, in which FIG. 1 is a perspective view of a high-voltage circuit breaker installation having four air blast circuit interrupter units connected in series; and

FIG. 2 is a simplified diagram partially in section, illustrating the principle of the mechanism used for controlling operation of the contacts in the interrupter units.

In FIG. 1 there is shown a layout of a high-voltage circuit breaker l0 incorporating the invention. This breaker consists of four separate interrupter units A, B, C, and D connected in series with each line 11, 12 of a multiline power supply. For example, a three-phase supply will have three such breakers A, B, C, and D interconnected for synchronized operation. Each interrupter unit is supported on the top of a column 13 of three post-type porcelain insulators 14, which column in turn stands on top of an upright base 15. For the most part, the four interrupter units A to D are substantially identical. Each consists essentially of a cylindrical metal tank 16 which houses the circuit-interrupting mechanism and contains a substantial volume of highly compressed dry air used for operating the mechanism and extinguishing the are produced when the contacts interrupt the current in line 11, 12. The tank rests on its side on insulator l4, and has attached to its ends porcelain bushings l7 and 18 which project well out from the tank and also well into it. A conductive rod passed coaxially through each bushing, beginning at a terminal on the outer end of the bushing and ending at a stationary interrupter contact fixed to the end of the bushing inside the tank. The bushing insulates the terminal, rod, and contact from the tank. As illustrated in FIG. 1, the interrupter units are connected in series. Unit A has the terminal on its bushing 17 connected to line conductor 11 and the terminal on its bushing 18 connected to the terminal on bushing 17 of unit B; The other terminal of unit B is connected to a terminal on unit C, and so forth from unit C to unit D to the terminal thereon connected to line conductor 12. The interconnections of the units possesses a fair degree of flexibility so that the units have some freedom of movement relative to one another, and they are covered by conductive shields 19 smoothly contoured to minimize corona discharge at the interconnections. A voltage grading ring 20 is provided for each one of the terminals of units A and D connected to line conductors l1 and 12. In each unit A to D, the movable contacts and the pneumatic mechanism for operating them comprise a single assembly located inside the tank directly above the insulating column 13. The tank is mounted on top of the column on a short exhaust pipe passing through the tank wall and fixed thereto. This pipe leads directly from the blast valve in the mechanism to an exhaust gas diffuser 21 attached to the column, the difiuser and pipe serving also as intermediate structure for supporting the tank on the column. Since the movable contacts and operating mechanism therefor are in direct metal-to-metal contact with the tank, the tank is at line potential when the contacts are closed. A voltage grading ring 22 is located directly below diffuser 21. Since the structure of the interrupter unit forms no part of the invention in itself, it will not be described in further detail except in so far as it relates to the controls for operating the unit. If further particulars are wanted on the structure of an interrupter unit suitable for use with the controls now to be described, reference may be had to the aforementioned U.S. Pat. No. 2,911,546, Oppel or to U.S. Pat. No. 2,783,338, Beatty.

The operation of the contacts of breaker 10 is controlled from a central control 23 located at the base of the structure in the middle thereof. Control 23 is linked operatively with a main control 24 located-at the top of columns 13 a little to one side of the row of columns directly above control 23. This linkage between controls 23 and 24 is located within astring of hollow insulators 25 aligned axially between controls 23 and 24. Control 24 has an actuator (not shown) for each one of the interrupter units A to D connected mechanically to a control valve such as 31 in FIG. 2 in the unit by mechanical means housed inside the strings 26, 27 of hollow insulators.

The string of insulators 26 extends horizontally in axial alignment to the left from control 24 to units A and B, to which it is connected. The string of insulators 27 extends horizontally in axial alignment to the right from control 24 to units C and D, to which it is connected. The joints between insulators 25, 26, 27 respectively and main control 24 and interrupter units A, B, C and D may be made with limited flexibility to allow for limited relative movement of the interrupter units. The columns of hollow insulators 25, 26, and 27 are also adapted to serve as air lines for conveying compressed air from a source located at the base of the breaker to the interrupter units. The details of the controls 23 and 24 form no part of the present invention. A sufficient understanding of the present invention can be had if it is understood that the controls 23 and 24, working together act to simultaneously operate all the control valves 31 in the units A, B, C, and D both during a circuit breaker opening operation and during a circuit breaker closing operation. A suitable mechanism for linking the control valves together for this type of operation in a three-unit circuit breaker is shown and claimed in application, Ser. No. 705,044, Barkan et al. filed Feb. 13, 1968.

It will be noted from FIG. 1 that a horizontal string of insulators 28 similar to 26, 27 appears on the other side of the row of interrupter units. This string houses the control rods which are a part of the mechanism for synchronizing the closing of the resistor switch contacts. It also possesses a degree of flexibility to allow for limited relative movement of the interrupter units, and is filled with the dry compressed air. The synchronizing means is the subject matter of this invention and will be described in connection with FIG. 2. Any metal joints between the insulators of strings 26, 27, and 28 are covered by corona shields 29 much like shields l9, and the metal joints between insulators 14 of columns 13 are shielded in the same way.

Referring now to FIG. 2, each interrupter unit A to D has the same type of pneumatic actuator for operating its main contacts and the same type of valve for controlling the operation of the actuator. However, only the actuator in unit D has a linkage associated therewith for controlling the closing of the resistor switches (soon to be described) in the various units. Thus the actuator in unit D acts as a master for controlling resistor switch-closing in units A to C in a way to be described later.

Each interrupter unit A to D, as shown for unit D in FIG. 2, has a pneumatic actuator 30, a valve 31 for controlling the operation of the actuator, and an assembly of main contacts 32 operated by the actuator. Actuator 30 consists essentially of a cylinder 33 and a two-piston component which has a relatively large piston 34 located inside the cylinder and a substantially smaller piston 35 projecting upward from piston 34 through the upper end wall of the cylinder. Seals are placed between the pistons and cylinder walls, and the upper end of the cylinder is vented to the atmosphere so that the top side of piston 34 is always at atmospheric pressure. The upper end of piston 35 carries a side arm 36 and is linked mechanically as indicated at 37 for operation of main contact assembly 32. Valve 31 is a two-position airflow control in which a disc 38 is moved up or down between valve seats 39 and 40 by means of a rod and bellcrank linkage 41. This linkage is operated by main control 24, and the main control is operated from central control 23.

In the position shown in FIG. 2, the disc of valve 31 is in its uppermost position against seat 39. Compressed air in the tank is now admitted to the lower end of cylinder 33 where it drives piston 34 into its uppermost position and in so doing opens the main interrupter contacts. During this time the upper end of piston 35 is also subjected to the full tank pressure, but since it is smaller in area than piston 34, the piston component moves up. When disc 38 is drawn down onto valve seat 40 by means of linkage 41 and the breaker controls 23, 24, the lower end of cylinder 33 is vented to the atmosphere through the valve and exhaust duct 39a. The compressed air in the tank continually urging piston 35 down now drives the piston component 35, 34 down, closing the interrupter contacts. Each unit of the four interrupter units A to D operates in this way through a two-position pneumatic actuator such as 30 and a valve such as 31 for selecting the actuator position. For reasons which soon appear more clearly, the exhaust duct 39a in unit D is made larger in cross section than the corresponding exhaust duct 39a in the other units and thus presents less impedance to the flow of exhaust gas therethrough. This allows the piston 34 of unit D to move downward during a closing operation more quickly than do the pistons 34 of the other units. During opening, the pistons 34 move upward at substantially the same speed.

In a series array of interrupter units such as A to D, it is known to equip each unit with a resistor and a switch for connecting the resistor across the main interrupter contacts a few milliseconds before the main contacts close and disconnecting the resistor a few milliseconds after the main contacts open. In other words, the resistors are connected in series with the power line a few milliseconds before the main interrupter contacts close, and they remain so connected until a few milliseconds after the main contacts open again. These resistors tend to reduce the magnitude of the voltage surges induced by the closure and interruption of electrical transmission systems.

The main contacts of interrupter units A to D are opened simultaneously and the resistor switches open simultaneously a few milliseconds later. They close in the following sequence: first, the main contacts of unit D close, followed immediately by the closing of the resistor switch of all four units; a few milliseconds later, the main contacts of units A, B and C close simultaneously. When the contacts in the circuit breaker are to be closed, valves 31 in all four units A to D are moved down onto the valve seats 40 so that the lower ends of all the cylinders 33 are vented to the atmosphere. The compressed air in the tanks acting on the upper end of the small pistons 35 now urge the piston components down in the direction of contacts closing. As the piston in unit D moves down, it actuates a resistor switch operating mechanism in unit D and also in each one of the other units A, B and C through a mechanical linkage operated by side arrn 36. Only the resistor switch operating mechanism in unit C is fully shown, and this is designated 42. A portion of the resistor switch operating mechanism 42 of unit D is shown, and this is connected to side arm 36 by a link 47a. The linkage for connecting side arm 36 to the resistor switch operating mechanisms of the other units A, B, and C consists of four bellcranks 43 to 46 and seven control rods 47 to 53 connecting arm 36 to an arm 54 in each one of the units A, B and C. As will soon appear more clearly the linkages 43-53 and mechanisms 42 close the resistor switches in a particular way and the actuators 30 close the main contacts. During interruption the mechanisms 42 cooperate with the actuators to keep the resistor switches closed until the main contacts have opened.

A resistor switch operating mechanism 42 is illustrated very simply in unit C, FIG. 2. It consists of an arm 54 pivoting on an axis 55 so as to drive a collar 56 down when rotated clockwise through downward movement of rod 49, which is pivotally attached to arm 54 at 57. Collar 56 is suitably guided so that it is moved down by arm 54 and up by a spring 58 tensioned between the collar and stationary frame structure 59. Its movement upward is normally limited by a latch 60 which pivots on a stationary axis 61 and is biased clockwise against a stationary stop 64 into a latched position by means of a spring 62 compressed between an arm on the latch and stationary structure 59. On piston 350 of actuator 30c approaching the upper limit of its travel, it engages a projection 63 on the latch and rotates the latch counterclockwise until it frees collar 56, whereupon spring 58 drives the collar up against the overhanging end of arm 54. Collar 56 carries a contacts-bridging member 65 suspended on a stem 66 which passes through the opening in the collar 56 and has a head 67 on its upper end that overhangs the upper surface of the collar. A spring 68 surrounding the stem and compressed between the collar and the bridging member biases the member against the stationary contacts 69 of the resistor switch. The arrangement of components 56 and 65 to 68 is such that once latch 60 releases the collar 56, spring 58 lifts the assembly far enough to fully open contacts 69 of the resistor switch. When the collar 56 is released, it moves into engagement with head 67 and thereby carries the other components with it. Resistor switch contacts 69 are connected across the main contacts 32c of the interrupter unit through resistors 71 and 72. The main contacts are operated by piston 35c of the actuator as indicated at 37c.

The contact-operating means of units A and B are constructed in the same way as that of unit C and operate in the same way. It is to be noted from FIG. 2 that resistor switch operating mechanism 42 is shown in a condition where it is about to be tripped while the main contacts 32c are shown open. Although not necessarily representative of the actual conditions, this has been done for purposes of illustrating the mechanism. Its tripped condition can be readily visualized without further illustration.

Arm 54 is rotated on its pivot 55 by means of the piston component of unit D through a mechanical linkage consisting of a rod 47, a bellcrank 43, a rod 48, a bellcrank 44 and a rod 49. The connections between the bellcranks and the rods are all pivotal joints, as are the connections of rods 47 and 49 with arms 36 and 54 respectively. Rods 50 to 53 and bellcranks 45 and 46 extend this operative connection to units B and A so that their resistor switch operating mechanisms operate to synchronism with the mechanism of unit C. Rods 48, 50 and 52 and bellcranks 43 to 46 are enclosed in the string of insulators 28 shown in FIG. 1, and the vertical rods 47, 49, 51 and 53 pass from the respective tanks through a neck 74 which extends from the tank to the string of insulators so that all of the breaker closing components operate in a compressed air environment. The rods will be made of a good insulating material such as glass fibers bonded together with an epoxy or polyester resin. Some of the rod ends will be adapted for length adjustment so that the operation of units A, B and C can be made simultaneous and synchronized with unit D. These will not be the only adjustable means; provision will be made for others as well.

When control 23 (FIG. 1) receives a signal to open the contacts in units A to D, it causes each of the control valves 31 to take its contacts-open position of FIG. 2, whereupon the pneumatic actuator in each unit is energized for contactsopening. During the opening stroke of unit D, arm 36 moves up with the piston component 35, 34, and in so doing it causes the arms 54 of units C, B and A to rotate counterclockwise until they are free of collars 56 as indicated in FIG. 2, after which pistons 35A, 35B and 35C trip latches 60 and free collars 56. so that they, under the influence of springs 58, now open the resistor switches. The timing of A, B and C with respect to D is such that they open their main contacts simultaneously, and after a few milliseconds delay the resistor switches open simultaneously.

When control 23 (FIG. 1) received a signal to close the contacts in units A to D, it causes each of the control valves 31 (FIG. 2) to take its contacts-closed position, i.e., disc 38 moves downwardly on to lower seat 40, whereupon the pneumatic actuator in each unit is energized for contacts-closing. The actuators of unit A to D immediately proceed to close their contacts. Duringthe closing stroke of unit D, arm 36 moves down with the piston component 35, 34, and in so doing it causes the arms 54 of units C, B and A and of its own unit D to rotate clockwise and reset mechanisms 42 to their latched positions where the resistor switches are closed. The timing of A, B and C with respect to D is such that D closes its main contacts first, followed immediately by the closing of all four resistor switches at the same time. A few milliseconds later the main contacts of units A, B and C close to complete the closing cycle. Unit D may be considered the master unit,

. and units A, B and C slave units because they have their contacts-closing operation controlled by events in unit D. In the contacts-closing operation, arm 36 may be regarded as a follower because it follows movement of piston component 34, 35, and, in so doing, it operates mechanisms 42 of units A, B,

C through the medium of linkage 43 to 53 and operates its own mechanism 42 through link 47a.

In summary, the sequence of opening the contacts is as follows:

The main contacts in all four units open independently and together. This connects the resistor in series with the line as the resistor switches are still closed. A few milliseconds later pistons 35A, 35B and 35C unlatch their mechanisms 42 and allow the resistor switches in units A, B and C open independently as piston 35 opens the resistor switch in.unit D.

The sequence of closing the contacts is somewhat different because the piston in unit D, during closing, operates faster than the pistons in units A, B and'C. The piston in unit D also provides the energy for synchronous closing of the resistor switches in units A, B, C and D due to its mechanical linkage with the resistor switches of these units. Closing is as follows:

The main contacts of unit D close first, followed immediately by synchronous closing of all four resistor switches. This connects the resistors of units A, B and C in series with the closed main contacts of unit D. A few milliseconds later the main contacts of units A, B and C close to complete the closing cycle.

Some of the advantages of the systemare believed to be as follows: (1) Mechanical operation of the resistor switches through a linkage 43-53 of the type described minimizes variations in closing times of the resistor switches. (2) The relatively short lengths of the control rods 47-53 in the linkage minimizes delays in translating a closing signal into closed contacts. Short rods also minimize the effects of harmonic oscillation that detract from the precision of synchronization. (3) The linkage has no live parts connected to ground through control media. (4) The scheme provides means for placing more resistance in the lineduring interrupter opening than during closing. A lower value of resistance for closing is more effective in reducing overvoltages when a long transmission line is energized with high voltage.

The expression simultaneous opening or closing of the main and resistor switch contacts".mentioned frequently in the disclosure and claims is intended to mean as nearly simultaneous as is physically possible having due regard to tolerances, the adjustments possible and conditions that influence interrupter operation.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and I, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a high-voltage circuit breaker comprising a plurality of separate circuit-interrupting units electrically connected together in series; each of said units comprising: separable main contacts, a resistor, a resistor switch connected in series with said resistor and closable to insert-said resistor in parallel with said main contacts, an actuator for opening and closing said main contacts, and means for energizing the actuator in one sense to close said main contacts and in another sense to open said main contacts; the combination of:

a. means connecting the resistor switch of one unit to the actuator of said one unit for transmitting closing force from said latter actuator to the resistor switch of said one unit for closing the resistor switch of said one unit in response to a main contact-closing operation of the actuator of said one unit after closing of the main contacts of said one unit,

b. linkage means connecting the resistor switches of said other units to the actuator of said one unit for transmitting closing forces from said latter actuator to said resistor switches of said other units for closing the resistor switches of said other units in response to a main contactclosing operation of the actuator of said one unit,

c. latching means for each of said resistor switches for latching each of said resistor switches closed,

. means associated with each of said units for unlatching its means in each unit for opening its resistor switch in response to unlatching of its latching means,

means for causing the actuator of said one unit to close its main contacts before the actuators of the other units close their main contacts and for causing the resistor switches of said other units to close before the main contacts of said other units close,

means for causing the actuators of said other units to close their main contacts substantially simultaneously after their resistor switches have closed, and

means for causing the actuators of all of said units to open their main contacts substantially simultaneously and to unlatch their respective latching means for substantially simultaneous opening of all of said resistor switches following opening of said main contacts.

The combination of claim 1 in which said linkage means comprises a linkage extending between said interrupting units and located entirely in a region of high potential approximating that of the line in which said circuit breaker is connected.

The combination of claim 1 in which:

each of said interrupting units comprises a tank which is at approximately line potential when the circuit breaker is closed and which houses the main contacts, the actuator, and the resistor switch of said unit,

. said linkage means comprises a mechanical linkage connected between the actuator of said one unit and the resistor switches of said other units,

insulating tubes are provided connected between said tanks, and

said mechanical linkage extends through said insulating tubes between said tanks.

The circuit breaker of claim 1 wherein each one of said units is a gas blast circuit breaker and said actuator is a pneumatic cylinder and piston, each unit comprising a compressed gas tank housing said actuator and said main contacts.

In a high-voltage circuit breaker comprising a plurality of said main contacts, and means for energizing the actuator in one sense to close said main contacts and in another sense to open said main contacts; the combination of:

a. means connecting the resistor switch of one unit to the b. linkage means connecting the resistor switches of said other units to the actuator of said one unit for transmitting closing force from said latter actuator to said resistor switches of said other units for closing the resistor switches of said other units in response to a main contactclosing operation of the actuator of said one unit,

. means for causing the actuator of said one unit to close its main contacts before the actuators of the other units close their main contacts and for causing the resistor switches of said other units to close before the main contacts of said other units close,

d. means for causing the actuators of said other units to close their main contacts substantially simultaneously after their resistor switches have closed, and

e. means for causing the actuators of all of said units to open their main contacts substantially simultaneously and to effect substantially simultaneous opening of all of said resistor switches following opening of said main contacts.

6. The combination of claim 5 in which said linkage means prises a linkage extending between said interrupting units ocated entirely in a region of high potential approximating that of the line in which said circuit breaker is connected.

7. The combination of claim 5 in which:

a. each of said interrupting units comprises a tank which is at approximately line potential when the circuit breaker is closed and which houses the main contacts, the actuator, and the resistor switch of said unit,

b. said linkage means comprises a mechanical linkage connected between the actuator of said one unit and the resistor switches of said other units,

0. insulating tubes are provided connected between said tanks, and

d. said mechanical linkage extends through said insulating tubes between said tanks.

i i i i 

1. In a high-voltage circuit breaker comprising a plurality of separate circuit-interrupting units electrically connected together in series; each of said units comprising: separable main contacts, a resistor, a resistor switch connected in series with said resistor and closable to insert said resistor in parallel with said main contacts, an actuator for opening and closing said main contacts, and means for energizing the actuator in one sense to close said main contacts and in another sense to open said main contacts; the combination of: a. means connecting the resistor switch of one unit to the actuator of said one unit for transmitting closing force from said latter actuator to the resistor switch of said one unit for closing the resistor switch of said one unit in response to a main contact-closing operation of the actuator of said one unit after closing of the main contacts of said one unit, b. linkage means connecting the resistor switches of said other units to the actuator of said onE unit for transmitting closing force from said latter actuator to said resistor switches of said other units for closing the resistor switches of said other units in response to a main contact-closing operation of the actuator of said one unit, c. latching means for each of said resistor switches for latching each of said resistor switches closed, d. means associated with each of said units for unlatching its latching means in response to its actuator operating its main contacts, e. means in each unit for opening its resistor switch in response to unlatching of its latching means, f. means for causing the actuator of said one unit to close its main contacts before the actuators of the other units close their main contacts and for causing the resistor switches of said other units to close before the main contacts of said other units close, g. means for causing the actuators of said other units to close their main contacts substantially simultaneously after their resistor switches have closed, and h. means for causing the actuators of all of said units to open their main contacts substantially simultaneously and to unlatch their respective latching means for substantially simultaneous opening of all of said resistor switches following opening of said main contacts.
 2. The combination of claim 1 in which said linkage means comprises a linkage extending between said interrupting units and located entirely in a region of high potential approximating that of the line in which said circuit breaker is connected.
 3. The combination of claim 1 in which: a. each of said interrupting units comprises a tank which is at approximately line potential when the circuit breaker is closed and which houses the main contacts, the actuator, and the resistor switch of said unit, b. said linkage means comprises a mechanical linkage connected between the actuator of said one unit and the resistor switches of said other units, c. insulating tubes are provided connected between said tanks, and d. said mechanical linkage extends through said insulating tubes between said tanks.
 4. The circuit breaker of claim 1 wherein each one of said units is a gas blast circuit breaker and said actuator is a pneumatic cylinder and piston, each unit comprising a compressed gas tank housing said actuator and said main contacts.
 5. In a high-voltage circuit breaker comprising a plurality of separate circuit-interrupting units electrically connected together in series; each of said units comprising: separable main contacts, a resistor, a resistor switch connected in series with said resistor and closable to insert said resistor in parallel with said main contacts, an actuator for opening and closing said main contacts, and means for energizing the actuator in one sense to close said main contacts and in another sense to open said main contacts; the combination of: a. means connecting the resistor switch of one unit to the actuator of said one unit for transmitting closing force from said latter actuator to the resistor switch of said one unit for closing the resistor switch of said one unit in response to a main contact-closing operation of the actuator of said one unit after closing of the main contacts of said one unit, b. linkage means connecting the resistor switches of said other units to the actuator of said one unit for transmitting closing force from said latter actuator to said resistor switches of said other units for closing the resistor switches of said other units in response to a main contact-closing operation of the actuator of said one unit, c. means for causing the actuator of said one unit to close its main contacts before the actuators of the other units close their main contacts and for causing the resistor switches of said other units to close before the main contacts of said other units close, d. means for causing the actuators of said other units to close their main contacts substantially simultaneously after Their resistor switches have closed, and e. means for causing the actuators of all of said units to open their main contacts substantially simultaneously and to effect substantially simultaneous opening of all of said resistor switches following opening of said main contacts.
 6. The combination of claim 5 in which said linkage means comprises a linkage extending between said interrupting units and located entirely in a region of high potential approximating that of the line in which said circuit breaker is connected.
 7. The combination of claim 5 in which: a. each of said interrupting units comprises a tank which is at approximately line potential when the circuit breaker is closed and which houses the main contacts, the actuator, and the resistor switch of said unit, b. said linkage means comprises a mechanical linkage connected between the actuator of said one unit and the resistor switches of said other units, c. insulating tubes are provided connected between said tanks, and d. said mechanical linkage extends through said insulating tubes between said tanks. 